Comet-combing Philae lander signs off for good

Philae carried out 80 percent of its planned initial scientific activities in the three days before it ran out of juice

It has been a long and drawn out farewell, but today the European Space Agency (ESA) will wave a final goodbye to its Philae lander, the first spacecraft to ever touch down on the surface of a comet. Mission control is shutting down communications to the lander resting on the surface of 67P/Churyumov-Gerasimenko, which is now around 520 million km from the Sun, and sending it off quietly into the night.

ESA is saying farewell to Philae in preparation for the end of the Rosetta mission. The Rosetta probe became the first spacecraft to enter orbit around a comet in August 2014 and has circled 67P/Churyumov-Gerasimenko ever since, snapping spooky photos and gathering all kinds of useful information on comet composition.

In November 2014, Rosetta sent its fridge-sized Philae lander toward the comet, but touchdown didn't play out as hoped. The onboard harpoons designed to anchor Philae in place failed to fire. This sent the craft tumbling across the surface of the comet until it came to rest in the shadows, where critically, its solar panels where unable to draw sunlight and charge up its batteries.

Philae carried out 80 percent of its planned initial scientific activities in the three days before it ran out of juice, but entered deep hibernation thereafter. Mission control has persisted in trying to re-establish contact with Philae, but some sporadic signals aside, the lander has remained incommunicado.

The Rosetta spacecraft will cease operations in September when it crashes gently into the surface of 67P/Churyumov-Gerasimenko. The ESA wants to direct every last smidgen of power towards this grand finale, where the probe will take once-in-a-lifetime measurements and images while up close and personal with the comet's surface.

Unfortunately for Philae, this means shutting down the Electrical Support System Processor Unit aboard Rosetta that the lander relies on to receive its signals. It had been left on just in case Philae managed to make contact again, but with Rosetta now losing around 4 W of power each day, the tough decision had to be made.